Marine vessels have long been used for commercial and military purposes. For example, commercial ships transport goods and tourists. As another example, military surface ships project power and deliver ordnance to targets, deliver military supplies and logistics, and transport military personnel. Further, military submarines deliver ordnance to targets and provide strategic deterrence from stealthy platforms. Finally, civilian and military marine vessels engage in scientific research of the ocean environment.
In some applications, it would be desirable to accomplish some of the objectives listed above through use of unmanned marine vessels. For example, use of an unmanned marine vessel to deliver ordnance, such as a torpedo, to a target would permit the ordnance to be delivered to the target without putting sailors in harm's way. However, currently known unmanned delivery vehicles produce large amounts of noise. As a result, currently known delivery vehicles may not bring significant amounts of stealth to a tactical situation. Thus, a target may gain a tactical advantage. Accordingly, effectiveness of currently known delivery vehicles may be diminished.
In order to maximize Mission effectiveness of unmanned marine vessels, it would be desirable to increase the amount of stealth enjoyed by the unmanned marine vehicle. Currently known submersible gliders, such as the Seaglider, can be considered stealthy submersible vehicles. The submersible gliders have high aspect ratio wings that impart a forward gliding to the glider as the glider experiences changes in ballast and their resultant changes in buoyancy.
Currently known underwater gliders can propel themselves for an extended period of time by modulating buoyancy through controlled ballasting. That is, gliders trade potential energy into work against drag. An underwater glider that is designed to be nearly-neutrally buoyant at the surface sinks very slowly. Therefore, the glider can attain extended range via its high lift-to-drag ratio that is largely achieved by its lifting surface. Once the glider attains its desired depth, internal air volume of the glider is increased, thereby lowering its density. This increases buoyancy force above weight of the glider, and the glider buoys upward to the surface of the sea. This phenomenon of using buoyancy to energize an underwater glider functions until ballasts are exhausted. That is, underwater gliding refers to motion in which the force of gravity provides propulsion, while steering is maintained typically by controlling location of the center of gravity of the vehicle.
Many currently known underwater gliders are used for oceanographic research, meteorology research, and deep-sea surveying. These currently known gliders used fixed wings for glide and pitch control and internal ballasts for depth and altitude control. For example, the “Slocum” glider uses ballast tanks to provide pitching moment's joint upward and downward glides and a sliding battery mass for fine adjustment of pitch and roll. With an operational range of 40,000 km, Slocum obtained its propulsive energy from thermal gradients in the water using a thermal engine that draws energy from ocean thermal clients (that is, temperature differences between warm surface water and cooler, deep water). Another currently known glider, “Spray,” has a range of 6000 km and has been developed and demonstrated under similar gliding principles to the Slocum. Apart from saving energy for propulsion, Spray lasts longer and operates more quietly than Slocum because of a lack of moving surfaces.
However, currently known gliders have limited glider range and applicability. For example, the Seaglider can attain speeds up to 0.5 knots at glide angles from 8° to 70° (1:5–3:1 slope). Because of the Seaglider's limited speed and glide capabilities, the Seaglider is limited to oceanographic research.
It would be desirable for an unmanned marine vehicle to provide for delivery of ordnance, supplies, personnel, or the like. However, internal capacities of currently known gliders are limited due to extensive components for ballasting and steering. Therefore, there is an unmet need in the art for an unmanned submersible transport system that provides desired stealth, speed, and other performance characteristics.